Method of fabricating a magnetic head by sputter etching

ABSTRACT

A floating type magnetic head is made of a polycrystalline material. A surface to be opposed to a magnetic recording medium is undulated with lands and grooves having a height difference of 50 to 200 Å on an average and a repetition pitch of 5 to 20 microns on an average. The portions, in which the heights of the lands and the grooves abruptly change, extend along the boundaries of the polycrystals. The head surface opposed to the magnetic recording medium is sputter-etched to have the predetermined surface roughness.

This is a divisional of copending application Ser. No. 07/360,124, filedon June 1, 1989, now U.S. Pat. No. 5,010429.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic head suitable for use incombination with a magnetic recording disk (or hard disk) and a processfor fabricating the same. More particularly, the present inventionrelates to a floating-type magnetic head and a process for fabricatingthe same.

2. Related Art Statement

The floating-type heads are described in U.S. Pat. No. 4,709,284 andU.S. Pat. No. 4,559,572. At present, most of the hard disks arefabricated as magnetic recording mediums by applying magnetic powder ofoxides to an aluminum alloy substrate. According to demand for the highrecording density of recent years, however, a hard disk fabricated byplating or sputtering the substrate with a magnetic material comes intouse. The magnetic disk becomes more small-sized and compact by using theplated or sputtered disk, and a drive source such as a motor for drivingthe disk becomes thinner and requires less torque.

The floating magnetic head constructed as described above is kept inlight contact with the magnetic disk by the force of a spring, while themagnetic disk remains at rest. While the magnetic disk is rotating, theair near the surface of the magnetic disk is similarly moved to exert aforce for lifting the lower surface of the slider. During the rotationof the magnetic disk, therefore, the magnetic head floats up and staysaway from the magnetic disk.

When the rotation of the magnetic disk starts and stops, the magnetichead slides on the magnetic disk. As regards the condition of thecontact to be established when the rotation of the magnetic disk isstopped, the flow of the air on the surface of the magnetic disk isslowed down gradually as the rotation of the magnetic disk is reduced.At the moment that the magnetic head is wholly derived of its buoyance,the magnetic head collides with the surface of the magnetic disk,rebounds thereon, and lands again on the surface of the disk. Afterrepeating this series of motions several times, the magnetic head isbrought to a stop as though it were dragged on the magnetic disk. Themagnetic head is required to withstand these impacts exerted thereonduring the start or stop of the rotations of the magnetic disk. Thisperformance may be referred to hereinafter as the CSS(Contact-Start-Stop) resistance property.

The disk surface prepared by the aforementioned plating or sputteringmethod is finished to acquire a better facial accuracy than that of theapplied type of the prior art. This causes a problem of sticking betweenthe head and the disk surface, although the problem is not serious inthe prior art. Specifically, as the facial accuracy of the surfacefacing the magnetic recording medium grows higher, the surface of thestationary disk and the opposed surface of the head will stick. If thissticking force between the head and the disk grows excessively strong,the life of the CSS resistance property of the device is shortened. Theproblem becomes serious especially for the device in which several disksare combined.

In order to solve that sticking phenomenon, a variety of treatmentsexist for making the surface of the head facing the disk coarse to someextent. However, none of them achieves sufficient effects.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetic head whichhas a small static friction coefficient with a disk and which issubstantially free from damages on the disk and head surfaces even afterthe repeated CSS so that it can have a high durability.

Another object of the present invention is to provide a process forfabricating this magnetic head.

A further object of the present invention is to provide a magnetic headwhich can reduce not only a friction to be established between itselfand the disk but also the size, weight and thickness of the disk deviceby an inexpensive, stable method.

A further object of the present invention is to provide a process forfabricating this magnetic head.

A further object of the present invention is to provide a floating-typemagnetic head which can reduce a friction to be established betweenitself and a sputtered or plated disk, thereby increasing the CSSresistance property so that the hard disk device can be small in size,light-weight and thin.

A further object of the present invention is to provide a process forfabricating this magnetic head.

According to an aspect of the present invention, there is provided afloating-type magnetic head of a polycrystalline material, whichcomprises a surface facing a magnetic recording medium and roughed toform lands and grooves having an average height difference of 50 to 200Å, an average repetition pitch of 5 to 20 microns, and their steepportions extending along the boundaries of crystals.

According to another aspect of the present invention, there is provideda floating-type magnetic head which comprises a surface facing amagnetic recording medium and composed mainly of lands having flatcrests and grooves having flat bottoms.

According to a further aspect of the present invention, there isprovided a floating-type magnetic head which comprises a surface facinga disk and finished to be wholly and partially undulated to have anaverage amplitude of 50 to 300 Å, as measured with a roughness curveusing a contact needle type roughness meter.

These magnetic heads are fabricated by a process which comprises thestep of finishing the surfaces of the magnetic heads facing the magneticrecording medium by a sputter etching to have a predetermined facialroughness.

According this process, during the sputter etching a layer having itsproperties changed may be removed, and the surface may be cleaned.

In this process, moreover, the surface facing the magnetic recordingmedium is masked except for its portion to be treated, so that only theportion outside the mask may be treated.

In this process using the mask, this mask may be removed during thesputter etching so that a step may be formed between the portion coveredwith the mask and the exposed portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2 and 3 are perspective views showing embodiments offloating-type magnetic heads according to the invention;

FIG. 4 is a perspective view showing a head chip for the embodiment ofthe magnetic head of FIG.;

FIG. 5 is a sectional view showing a bearing surface of the magnetichead;

FIGS. 6, 7, 8, 10 and 11 are graphs presenting the individual results ofmeasurement; and

FIG. 9 is a microscopic photograph taken from the bearing surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, the magnetic head may be of a monolithic orcomposite type.

FIG. 1 is a perspective view showing one embodiment of a monolithic typemagnetic head 10. A slider, designated by reference numeral 1, is formedwith two ridges of main bearing surfaces 2 and 3 at its side portions.The slider 1 is further formed with a thin bearing surface 4 whichextends in the form of a ridge in parallel with the main bearingsurfaces 2 and 3. A core 6 is bonded to the read end portion of thebearing surface 4 through a magnetic gap 5. The bonded surfaces (i.e.,front and back gaps) of the core 6 and the slider 1 may be formed with athin film of an alloy having a high magnetic permeability. A winding isaccomplished through a winding aperture 7 to provide a predeterminednumber of turns on the core 6.

Here, the magnetic alloy of high magnetic permeability may be suitablyexemplified by an Fe-Al-Si alloy, usually referred to as "Sendust". Anespecially suitable magnetic alloy of Fe-Al-Si contains 2 to 10 wt. % ofAl and 3 to 16 wt. % of Si, the remainder being substantially Fe. Themost suitable one contains 4 to 8 wt. % of Al and 6 to 11 wt. % of Si,the remainder being substantially Fe. Incidentally, the magnetic alloymay suitably contain 2 wt. % or less of Ti or Ru because the corrosionand wear resistance can be improved. Similar effects can be obtainedeven if 4 wt. % or less of Cr is contained therein.

On the other hand, a magnetic alloy of highly magnetic permeability mayalso be exemplified by an amorphous alloy of Co-Nb-Zr (e.g., 70 to 90 at% of Co, 5 to 20 at % of Nb and 2 to 10 at % of Zr).

FIG. 3 is a perspective view showing one embodiment of a composite typemagnetic head 11. Magnetic head 11 is composed of a slider 12 and amagnetic core 13 called the "chip". The slider 12 is made of a magneticor nonmagnetic material. The core 13 is fixedly molded of glass in aslit 16 which is formed in one bearing surface 14 of two bearingsurfaces 14 and 15 of the slider 12.

The detailed structure of one example of the core 13 is shown in FIG. 4.In FIG. 4, sputtered films 22 and 23 are formed over a C-shaped core 20and an I-shaped core 21. These C-shaped core 20 and the I-shaped core 21are glass-bonded to leave a gap 24. Numeral 25 designates the glass.Moreover, the I-shaped core 21 has a winding aperture 26 to provide apredetermined number of turns of a winding.

The aforementioned C-shaped core 20 or I-shaped core 21 may be suitablymade of a polycrystalline magnetic ceramic material such as Mn-Znferrite, Ni-Zn ferrite or a Mn-Ni oxide ceramic material, of which theMn-Zn ferrite is the most suitable. The composition of the suitableMn-Zn ferrite may be exemplified by 25 to 37 mol % of MnO, 8 to 23 mol %of ZnO and 51 to 57 mol % of Fe₂ O₃.

The aforementioned slider 1 or 12 may be suitably made of either: apolycrystalline magnetic ceramic material such as Mn-Zn ferrite, Ni-Znferrite or a Mn-Ni oxide ceramic material (of NaCl type); or anon-magnetic ceramic material such as calcium titanate, barium titanate,alumina or zinc ferrite. The slider 1 or 12 may naturally be made of amaterial other than the above-specified ones. Incidentally, the Mn-Nioxide ceramic material may desirably be composed of 51 to 66 mol % ofMnO, 34 to 49 mol % of NiO, and 1 to 15 mol % of one or two kinds of Al₂O₃, ZrO₂, CaO and Y₂ O₃.

In the present invention, the aforementioned bearing surfaces 2, 3, 4,14 and 15 are treated to have a predetermined facial roughness. Whilethe head 10 or 11 is in its normal stop position, the bearing surfaces2, 3, 4, 14 and 15 comes into actual contact with the disk in thestationary state in a region A (other than slopes B and C formed at thefront and rear edges of the head), as shown in FIGS. 1 and 3. In thepresent invention, all of those regions A, B and C may be treated tohave the aforementioned specific facial roughness, but normally only theregion A is treated. Alternatively, only a major portion of the region Asuch as a region T, as dotted in FIG. 2, may be treated.

FIG. 5 is a schematic section showing the bearing surfaces of the head.In the bearing surfaces, as shown, there alternately appear lands 28 andgrooves 29, between which there appear steep portions 30 having abruptheight changes. These steep portions 30 extend along the boundaries 42of crystals 31 through 41. The height differences d between the lands 28and the grooves 29 are within 50 to 300 Å, as measured by a roughnessmeter, and have an average value of 50 to 200 Å (preferably 70 to 170Å). The repetition pitch e of the lands and grooves is 5 to 20 microns(preferably 7 to 17 microns).

The sticking phenomemon of the head and the disk is prevented orreleased by forming the suitable steps between the lands 28 and thegrooves 29 and by repeating the steps at the suitable pitch. Moreover,the extensions of the steep portions 30 along the crystal boundaries 42is thought to prevent the disk from CSS damage. Since the steep portions30 extend along the crystal boundaries, more specifically, they aregiven a strength substantially similar to that of the single crystalparticles so that no cracking will be caused even if the edges of thesteep portions repeatedly (more than several ten thousands times)collide with the disk. The reason why the disk is not damaged is thoughtto come from the fact that no sharp portion or particle is formed as aresult of cracking.

Since, in the present invention, the bearing surfaces are formed mainlyof flat crests and flat bottoms, the head is reliably avoided fromscratching the disk surface when the head lands or rebounds on the disksurface, so that the CSS resistance property can be improved.

The static friction coefficient μ₁ between the disk and the head can beheld at 1.0 or less, desirably at 0.7 or less. This static frictioncoefficient was determined by forcing the magnetic head onto thestationary magnetic disk by the force of about 8 g-f (7,840 dynes) tomeasure the force (or torque) required for starting the rotation of themagnetic head and by converting the measured force into the frictioncoefficient.

These bearing surfaces may be formed by a sputter etching, as will bedescribed hereafter. In case the bearing surfaces are to be treated bysputter etching, a floating-type magnetic head can achieve the objectsof the present invention, if it is finished such that the whole orpartial portions of the bearing surfaces are undulated to have anamplitude of 50 to 300 Å, as measured by a roughness curve using acontact needle type roughness meter.

The sputter etching is a method for roughing the surface of the magnetichead opposed to the disk by means of a sputtering apparatus. Theordinary sputtering method is accomplished by ionizing inert gases suchas Ar (argon) gases under a high voltage so that the surface of a target(i.e., substrate) may be bombarded with the Ar ions to stick the targetparticles to the other portions of the substrate, thereby forming a filmthereon. In the sputter etching, on the other hand, the magnetic headsurface is bombarded with the ionized inert gases to etch the atoms onthe head surface. Here, the head is made of a polycrystalline materialcomposed of fine crystals. The individual crystal particles composingthe head have different planar orientations so that the head surface isetched as it is bombarded with the ionized gases. Because of thedifference of the planar orientations, the atomic bonding energies aredifferent in the individual crystal directions so that the energiesrequired for etching the surface are different. In this etching process,the amounts of the crystal particles to be etched are different so thatfine steps are formed among the individual particles. This sputteretching is an atomic treatment for controlling the sizes of steps fromfiner to relatively larger ones according to the etching time.Incidentally, during the sputter etching, the treated layers are removedfrom the surface being cleaned. For the sputter etching, moreover,unnecessary portions are masked so that only the necessary portions maybe sputter-etched.

EXAMPLE 1

The monolithic type magnetic head shown in the perspective view of FIG.1 was made of Mn-Zn polycrystalline ferrite containing 31 mol % of MnO,16 mol % of ZnO and 53 mol % of Fe₂ O₃. The surface of the head to beopposed to the disk was mirror-polished to have a surface roughness of10 to 40 Å by means of a wet lap using fine grinding particles ofdiamond.

The surface of this monolithic type magnetic head to be opposed to thedisk was sputter-etched with Ar gases under a pressure of 0.44 to 0.48Pa by means of an etching apparatus of an R-F type, in which theturntable had a diameter of 42 cm and a making power of 0.5 KW.

FIG. 6 is a graph plotting the relation between the sputter etching timeand the surface roughness. Although this relation depends upon themaking power, the kind, composition and pressure of the inert gases, theroughness changes substantially in proportion to the time with a varyinggradient. The etching amount of the surface at this time is also plottedin FIG. 6. Since the head surface was masked to have a thickness morethan that to be etched, it was not wholly removed but partially left atits portions unmasked so that a head having a partial contact with thedisk could be fabricated, as shown in FIG. 2. Moreover, the slidersurface could be prevented from direct contact with the disk by removingthe mask in the course of the sputter etching to enlarge the steps ofthe slider surface opposed to the disk while reducing the remainingopposed surface, thereby forming other steps in-between.

FIG. 7 is a graph plotting the changes in the static frictional force,which was established between the disk and the head when the stepsbetween the lands and grooves of the head were changed, against thenumber of repetitions of the CSS. In the prior art using the wet laptechnique, the frictional force was increased with the repetition numberof the CSS and was found to jump from about ten thousands times. In thehead having the lands and grooves of the present invention, on thecontrary, the increase in the frictional force was acceptable. Thisimplies that the resultant effect will be the better for the roughersteps of the head surface opposed to the disk. If, however, this surfaceis excessively roughed, there arises a problem that the head and thedisk will be damaged. Therefore, the difference between the lands andthe grooves for causing no damage will determine the upper limit.

EXAMPLE 2

The floating-type magnetic head used was mirror-finished to 10 to 40 Å.This magnetic head was set in position on the turntable (having adiameter of 42 cm) of the same R-F magnetron type sputter apparatus. Thesurface of the magnetic head to be opposed to the disk was treated witha making power of 0.3 to 1.0 KW, under an Ar gas pressure of 0.4 to 0.5Pa and for a sputter etching time of 10 to 60 mins. The floating typemagnetic head thus fabricated according to the present invention isshown in FIG. 2. Here, the dotted portion shown in FIG. 2 is thattreated by the sputter etching, and the remaining portion was masked andleft untreated. The CSS resistance properties of the sputtered disk andthe plated disk were measured to confirm that the static frictioncoefficient μ₁ could be held at 0.7 or less even for the repetitionnumber of the CSS of thirty thousands or more, if the difference betweenthe lands and the grooves was 50 to 300 Å (or 50 to 200 Å on anaverage), so that both the sputtered and plated disks were not crushed.

EXAMPLES 3 AND 4 AND COMPARISONS 1 AND-2

The sputter etching time of the Example 1 was set at 0 mins (forComparison 1), 10 mins (for Example 3), 20 mins (Example 4) and 30 mins(for Comparison 2). The surface roughness curves obtained of the bearingsurfaces are shown in FIGS. 8(a)-(d). The depth d and pitch e (asdefined with reference to FIG. 5) of these cases are enumerated in thefollowing Table:

    ______________________________________                                        No.             d.sub.max (Å)                                                                      e (microns)                                          ______________________________________                                        Comparison 1     30      3 to 10                                              Example 3       100      5 to 20                                              Example 4       180      5 to 20                                              Comparison 2    350      5 to 20                                              ______________________________________                                    

Incidentally, the microscopic photograph of the bearing (or treated)surface of the Example 1 is shown in FIG. 9.

CSS Test 1

The CSS test was conducted by using the heads of the Examples 3 and 4and the Comparisons 1 and 2.

The disks used in the CSS test are the following hard disk of 3.5inches:

Substrate: Aluminum;

Surfacing Layer: Cr;

Magnetic Layer: Co-Ni sputtered film;

Surface Layer: Lubricant layer (having a thickness of about 10 to 30 Å)of a fluorine resin applied to the surfaces of the C-sputtered layer andthe C-layer; and

Disk Surface Roughness: 400 to 600 Å.

The disk driving conditions for the CSS test were as follows:

Rotating Speed: 3,600 r.p.m.;

Period for One Rotation: 7 secs; and

Stop Time between Rotations: 3 secs.

The static friction coefficient μ between the head and the disk wasmeasured while the CSS test was being conducted.

The results are shown in FIG. 10, together with the repetition number ofthe CSS.

The following results can be found from FIG. 10:

The static friction coefficient μ even after the CSS of one hundredthousands was about 0.6 or less in the Examples 3 and 4, and neither thedisk nor the head was abnormal. In the Comparison 1, the head and thedisk chattered after the CSS of ten thousands, when they came intocontact, and caused failures at the start of the disk rotations afterthe CSS of forty thousands. In the Comparison 2, the static frictioncoefficient μ was low, and both the head and disk surfaces were damagedafter the CSS of twenty thousands.

CSS TEST EXAMPLE 2

The testing items were similar to those cf the foregoing test except forthe use of the following plated disk:

Substrate: Aluminum;

Surfacing Layer: Ni-P;

Magnetic Film: Co-Ni; and

Surface Layer: C and lubricant (identical to that of the Test Example1).

The results of this CSS test Example are shown in FIG. 11, from which itis found that the results obtainable were similar to those of the testExample 1.

EXAMPLE 5

The slider 12 of the composite type magnetic head 11, as shown in theperspective view of FIG. 3, was made of Mn-Zn polycrystalline ferritecontaining 31 mol % of MnO, 16 mol % of ZnO and 53 mol % of Fe₂ O₃, andits air-bearing surfaces 14 and 15 were mirror-finished to have asurface roughness of 10 to 40 Å. These air-bearing surfaces weresputter-etched for about 15 mins under the same conditions as those ofthe Example 1. As a result undulations having land and groovedifferences of about 150 Å were formed along the boundaries of the Mn-Znferrite crystals. The CSS resistance properties of the sputtered andplated disks were measured by the use of the magnetic head to revealthat the static friction coefficient μ₁ was about 0.5 to 0.6 even afterlapse of the CSS repetition times of one hundred thousands.

EXAMPLE 6

The slider 12 of the composite type magnetic head 11, as shown in theperspective view of FIG. 3, was made of a MnO-NiO nonmagnetic ceramicmaterial having a NaCl crystal structure and containing 58 mol % of MnO,38 mol % of NiO and 4 mol % of Al₂ O₃. The resultant air bearingsurfaces 14 and 15 were sputter-etched for 15 mins under the sameconditions as those of the Example 1. As a result, undulations havingthe maximum land and groove differences of 180 Å (or 120 Å on anaverage) were formed along the crystal boundaries of the Mn-Ninonmagnetic ceramic material. The CSS resistance properties of thesputtered and plated disks were measured by the use of the magnetic headto reveal that the static friction coefficient μ₁ was about about 0.4 to0.6 even after lapse of the CSS repetition times of one hundredthousands.

What is claimed is:
 1. A process for fabricating a magnetic head,comprising the steps of:setting a slider of a polycrystalline ceramicmaterial in a sputtering apparatus; sputter-etching at least one portionof said slider surface to be opposed to a magnetic recording disk, bygenerating ionized gases in at least one portion of said opposed slidersurface, so that lands and grooves may be formed to have a difference of50 to 200 Å on an average and a repetition pitch of 5 to 20 microns onan average; and bonding a magnetic core to said slider.
 2. A magnetichead fabricating process according to claim 1, wherein saidsputter-etching step removes a property-changed layer from the surfaceof said slider and cleans said slider surface.
 3. A magnetic headfabricating process according to claim 1, further comprising the step ofmasking that portion of the slider surface opposed to said magnetic diskother than a portion thereof to be treated, so that only the portionexposed from the mask may be sputter-etched.
 4. A magnetic headfabricating process according to claim 3, further comprising the step ofremoving said mask during said sputter-etching step to form stepsbetween the masked and exposed portions.
 5. A magnetic head fabricatingprocess according to claim 1, wherein said sputter-etching step formsundulations of said lands and said grooves having an amplitude of 50 to300 Å.
 6. A magnetic head fabricating process according to claim 1,wherein the ceramic material composing said slider is spinel typeferrite.
 7. A magnetic head fabricating process according to claim 1,wherein the ceramic material composing said slider is Ni-Zn ferrite orMn-Zn ferrite.
 8. A magnetic head fabricating process according to claim1, wherein the ceramic material composing said slider is an Mn-Ni oxide.9. A magnetic head fabricating process according to claim 1, wherein theceramic material composing said slider is calcium titanate, bariumtitanate, alumina, or zinc ferrite.
 10. A magnetic head fabricatingprocess according to claim 1, wherein the lands and grooves are formedto have a difference ob 70 to 170 Å on an average and a repetition pitchof 7 to 17 microns on an average.
 11. A magnetic head fabricatingprocess according to claim 1, wherein steep portions are formed betweenthe lands and grooves extending along the boundaries of the ceramicmaterial crystals.
 12. A magnetic head fabricating process according toclaim 1, further comprising, prior to said sputter-etching step, thestep of polishing the slider surface to be opposed to the disk.
 13. Amagnetic head fabricating process according to claim 12, wherein in thepolishing step the slider surface is polished to have a surfaceroughness of approximately 10 to 40 Å.
 14. A magnetic head fabricatingprocess according to claim 13, wherein the undulations extend along theboundaries of the ceramic material crystals.